全文获取类型
收费全文 | 97875篇 |
免费 | 3109篇 |
国内免费 | 2539篇 |
专业分类
化学 | 39615篇 |
晶体学 | 1070篇 |
力学 | 7703篇 |
综合类 | 187篇 |
数学 | 33751篇 |
物理学 | 21197篇 |
出版年
2023年 | 270篇 |
2022年 | 480篇 |
2021年 | 600篇 |
2020年 | 680篇 |
2019年 | 682篇 |
2018年 | 10821篇 |
2017年 | 10653篇 |
2016年 | 6869篇 |
2015年 | 1673篇 |
2014年 | 1349篇 |
2013年 | 1789篇 |
2012年 | 5557篇 |
2011年 | 12245篇 |
2010年 | 6904篇 |
2009年 | 7130篇 |
2008年 | 7942篇 |
2007年 | 9894篇 |
2006年 | 1391篇 |
2005年 | 2382篇 |
2004年 | 2387篇 |
2003年 | 2721篇 |
2002年 | 1845篇 |
2001年 | 806篇 |
2000年 | 780篇 |
1999年 | 580篇 |
1998年 | 503篇 |
1997年 | 428篇 |
1996年 | 491篇 |
1995年 | 376篇 |
1994年 | 288篇 |
1993年 | 289篇 |
1992年 | 228篇 |
1991年 | 213篇 |
1990年 | 185篇 |
1989年 | 166篇 |
1988年 | 153篇 |
1987年 | 125篇 |
1986年 | 122篇 |
1985年 | 123篇 |
1984年 | 81篇 |
1983年 | 73篇 |
1982年 | 70篇 |
1981年 | 66篇 |
1980年 | 64篇 |
1979年 | 58篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
A pressure sensitive paint (PSP) measurement has been known as a pressure field measurement technique based on the oxygen quenching phenomenon of luminescence of specific luminophores. A PSP measurement was applied for pressure field measurement in a low-solidity circular cascade diffuser of a single-stage transonic centrifugal compressor with 5 in pressure ratio for HFC134a gas. The oxygen concentration was about 500 ppm. Ru (bath-phen) was adsorbed on a silica-gel thinlayer chromatography sheet, and the sheet was pasted onto the side-wall between the cascade vanes. A drastic change in luminescent intensity was recognized during a surge condition. Also the pressure variations based on luminescent intensity agreed well with the pressure fluctuations measured using a semiconductor pressure sensor with high-frequency-response. It was shown that a PSP measurement worked well to investigate the unsteady pressure fields in a circular cascade diffuser of a transonic centrifugal compressor. Moreover, the time response of PSP becomes clear as a problem to be overcome for the present. 相似文献
52.
53.
54.
Dual fractional cutting plane algorithms, in which cutting planes are used to iteratively tighten a linear relaxation of an integer program,
are well-known and form the basis of the highly successful branch-and-cut method. It is rather less well-known that various primal cutting plane algorithms were developed in the 1960s, for example by Young. In a primal algorithm, the main role of the cutting
planes is to enable a feasible solution to the original problem to be improved. Research on these algorithms has been almost
non-existent.
In this paper we argue for a re-examination of these primal methods. We describe a new primal algorithm for pure 0-1 problems based on strong valid inequalities and give some encouraging computational results. Possible extensions to the case of general
mixed-integer programs are also discussed. 相似文献
55.
56.
Yasuyuki Kawahigashi 《Communications in Mathematical Physics》2002,226(2):269-287
We study the recent construction of subfactors by Rehren which generalizes the Longo–Rehren subfactors. We prove that if
we apply this construction to a non-degenerately braided subfactor N⊂M and α±-induction, then the resulting subfactor is dual to the Longo–Rehren subfactor M⊗M
opp⊂R arising from the entire system of irreducible endomorphisms of M resulting from αplusmn;-induction. As a corollary, we solve a problem on existence of braiding raised by Rehren negatively. Furthermore, we generalize
our previous study with Longo and Müger on multi-interval subfactors arising from a completely rational conformal net of factors
on S
1 to a net of subfactors and show that the (generalized) Longo–Rehren subfactors and α-induction naturally appear in this context.
Received: 11 September 2001 / Accepted: 7 October 2001 相似文献
57.
Julio Castellanos 《Mathematische Zeitschrift》2002,239(4):777-802
We consider complete ideals supported on finite sequences of infinitely near points, in regular local rings with dimensions
greater than two. We study properties of factorizations in Lipman special *-simple complete ideals. We relate it to a type
of proximity, linear proximity, of the points, and give conditions in order to have unique factorization. Several examples
are presented.
Received: 2 February 2000 / in final form: 14 March 2001 / Published online: 18 January 2002 相似文献
58.
59.
60.
Alexander Krasnosel'skii Dmitrii Rachinskii 《NoDEA : Nonlinear Differential Equations and Applications》2002,9(1):93-115
We consider autonomous systems with a nonlinear part depending on a parameter and study Hopf bifurcations at infinity. The
nonlinear part consists of the nonlinear functional term and the Prandtl--Ishlinskii hysteresis term. The linear part of the
system has a special form such that the close-loop system can be considered as a hysteresis perturbation of a quasilinear
Hamiltonian system. The Hamiltonian system has a continuum of arbitrarily large cycles for each value of the parameter. We
present sufficient conditions for the existence of bifurcation points for the non-Hamiltonian system with hysteresis. These
bifurcation points are determined by simple characteristics of the hysteresis nonlinearity. 相似文献